Copper base alloy



Patented Apr. 15, 1941 UNITED COPPER BASE ALLOY and M. Kelly, Traflord, Pa., assignor to Westinghouse Electric A; Manufacturing Company,

East Pittsburgh, Pa., a corporation of Pennsyl- Vania I No Drawing. Application Fcbruary'18, 1939,

Serial No. 257,145 4 Claims. (Cl. 1411-32) Thisinvention relates to alloys and particulars ly to copper base alloys which have good me= chanicalpthermal and electrical properties and the utilization of the alloys as articles of manufacture. t

In my prior application Serial No. 149,146, filed June 19,' 1937, now issued as Patent No. 2,147,844, and assigned to the assignee of this invention, there is disclosed and claimed an improved copper base alloy of copper. cobalt and iron. The alloys disclosed therein are quite satisfactory and have unusual ductility. However, it has been observed that even though the copper-cobalt-iron alloys have an unusual ductility, they show a low elongation when fractured in tension, the fracture being of the shear-type rather than the'usual neckdown fracture ordinarily expected. Further, it has also been observed that the copper base alloys disclosed in Patent No. 2,147,844 are not alwaysfree machining, and that they are some times dimcult to extrude.

An object of this invention is to provide a cophave the cobalt and iron present in the copper base'in a ratio of between .5 and 1.25 to 1. A more detailed description of the ternary copper, cobalt and iron alloy may be had by reference to the aforesaid patent, I

In order to improve the basic copper, cobalt and iron alloy, it has been found to be desirable to p I stood, it is apparent from the results obtained with an alloy containing lead, as hereinafter deacteristic 'of high physical strength and good A further object of this invention is to utilize the copperbase alloys formed to shape and precipitation hardened to give high physical strength and good electrical and thermal conductivity.

A more specific object of this invention is to provide acopper base alloy having the characteristic of being free machining, .free from sheartype fracture, sufiiciently plastic for extrusion work, free from columnar crystal growth, and of being susceptible to precipitation hardening to give high physical strength and good electrical and thermal conductivity. Y

Other objects of this invention will become apparent from the following description and the appended claims.

In order to produce copper base alloys which will have desired mechanical and electrical properties,metals which can be precipitated to effect a fine dispersion of fine particles throughout a copper base when suitably heat treated are added to the copper melt. In my Patent No.

2,147,844, issued February 21, 1939, there is disclosed a copper base alloy comprising copper, .cobait and iron with the cobalt andiron content ranging from a small but effective amount up to 5% of each and in which is preferred to a small but effective amount up to 5% and the balance substantially all copper, the lead content depending upon the characteristics desired in the alloy. 1

Where it is desired to produce an alloy which 'is free machining, lead is included in the coppercobalt-iron alloy in anamount ranging from .1% 'to3%. The upper limit of 3%, however, may be varied'somewhat, it being found through experiment that 3% is sufllcie'nt inanyof the combinations possiblewhere the cobalt and iron content ranges up to 5% of each, 'to impart the characteristic of being free machining to the alloy of this invention. The presence of lead within the range given is sufilcient' to break up the continuity of the chips when the resulting alloy is machined,

"thereby rendering the alloy easy to be'worked where delicate machining is necessary. Such improvements in the machining characteristics of the resulting alloy isobtained without sacrifice -'as to hardness and conductivity.

By including lead within the range'of from .05

that the elongation characteristics of the copper base alloy are greatly improved. When the copper base alloy containing lead is tested for elongation characteristics, it is found that a desired neckdown fracture occurs, as compared to the shear type fracture found in the copper-cobaltiron alloys which do not contain lead; In practice, about .2% of lead is preferred where elongation is the only characteristic which it is desired to improve.

This copper-cobalt-iron-lead"alloy having a lead content of up to 3% is also found to be sufficiently plastic for extrusion work where it is necessary to force the alloy through dies in. forming it to a desired shape. For imparting plasticity to the alloy, it is desired that the lead be present in amounts ranging from 1% to 3%, this amount having been found to be satisfactory for imparting plasticity to the alloy with the added .5% with the cobalt and iron within the rangesgiven hereinbefore, is satisfactory for inhibiting the columnar crystal growth in the copper base alloy and renders the alloy especially suitable for the making of sand castings in foundry work.

The copper base alloy containing cobalt, iron and lead within the ranges given hereinbefore may be cast in massive, intricate or fine form in any suitable type of molding, such as chill cast mold and particularly sand casting. Where desired, the alloy may be cast directly into the predetermined shape of the article which is to be manufactured, after which, because of the inclusion of lead, it may be easily machined as required, or it may be cast to a pattern suitable for forging or extruding to the desired shape. In the cast condition, the copper-cobalt-iron-lead alloy is comparatively ductile, having good elongation characteristics and may be easily forged or drawn to shape.

The alloy of this invention issusceptible to age hardening and, when subjected to a heat treatment comprising quenching from a high temperature of between 750 C. and the melting point of the alloy, followed by a reheat or ageing at a temperature of between 450 C. and 600 C. with or without an intermediate cold working step, is found to have high physical strength and good electrical and thermal conductivity.

As anexample of the improvement in the conductivity and hardness of the copper base alloy containing cobalt and iron by the inclusion of lead, the following is given as a specific example, corresponding improvements being found in other alloys containing the cobalt, iron and lead within the ranges given hereinbefore. As quenched from a temperature of 1000 C. and aged for hours at 500 0., a copper base alloy containing 1% cobalt and 1% iron is found to have a conductivity of 60% of that of pure copper and a Rockwell B hardness of 72, whereas an alloy subjected to the same heat treatment and having the same cobalt and iron content with the addition of 2% of lead has a conductivity of 66% of that of pure copper and'a Rockwell'B hardness of '74, while a further increase of lead content of up to .6% with the cobalt and iron contents the same as before ave a conductivity of 68% and. a Rockwell B hardness of 77, when subjected to the same heat treatment.

It is not known exactly what reaction takes place in the alloy due to the lead additions to cause such an unexpected increase in the conductivity and hardness, but as a possible explanation, it is thought that perhaps the lead reacts with both the iron and cobalt in the alloy in cobalt products to come out of solution during the ageing to give this unexpected result. In other alloys containing the cobalt, iron and lead within the ranges given hereinbefore, an improvement of about 5% in hardness and approximately 10% in conductivity is obtained over the copper, cobalt and iron alloy which does not contain the lead additions and which is subjected to identical conditions ofcasting and heat treatment.

In castings of the alloy of this invention containing up to 10% of lead, such as for bearing applications or the like, it is noted that the iron and cobalt of the alloy apparently has an effect on the lead, distribution in the cast alloy. The presence of the iron and cobalt appears to cooperate with the lead to effect a very uniform distribution of lead in the alloy giving a microstructure of a copper alloy matrix having spherical lead particles distributed uniformly therein. Thus the tendency of lead to segregate in these copper alloys, as observed in many other types of copper base alloys, due to its higher density and its insoluble nature both in the liquid and solid state, is overcome by the presence of, and through the cooperation with, the iron and cobalt alloying constituents and an alloy is provided which may find wide and varied applications. It is thought that the uniform distribution of the lead in the alloy renders the alloy of this invention particularly applicable to bearing structures, since the lubrication characteristics of the alloy is apparently improved by the distribution of the lead. Further, since the alloys containing the uniform distribution of the lead are susceptible to precipitation hardening, the high strength characteristics of the alloy may be utilized to give an extremely strong bearing structure.

The allow of this invention may be employed in many applications, such as in the manufacture of large castings, electrical applications, such as welding wheels, or other articles where a conductivity of or greater is required together with high physical strength. These alloys may also be efficiently employed in applications such as cylinder heads for internal combustion engines where high thermal conductivity is desired combined with high physical strength. Further, because the alloy has the desired free machining characteristic, the plasticity necessary for extrusion, is resistant to columnar crystal growth and is susceptible to precipitation hardening, it may be employed in many varied applications such as screw machine stock, cast valves of different sizes and shapes, bearings, gears, hardware and switchgear applications.

It is, of course, to be understood that this invention is described with reference to a specific such a manner as to cause the resulting iron and embodiment thereof and that other and various modifications may be made without in any way departing from the spirit of the invention as set forth in the appended claims.

I claim as my invention:

1, An alloy comprising from a small but effective amount up to 5% of cobalt, from a small but effective amount up to 5% of iron, from .05% up to 10% of lead, and the balance substantially all copper.

2. An alloy comprising from a small but effective amount up to 5% of cobalt, from a small but efiectiveamount up to 5% of iron, from .05%

up to 3% of lead, and the balance substantially all copper. I

3. An alloy comprising from a small but eifective amount up to 5% of cobalt, from a small but effective amount up to 5% of iron, from 135% up to 10% of lead, and the balance substantially all copper, which has been quenched from a temperature of between 750 C, and the melting point of the alloy and aged at a temperature of loetween 450 C. and; Gill? CL 4. As an article of manufactuman alloy comprising from a. small but effective amount up to 5% of cobalt, from a. small out effective amount .to a predetermined shape; and precipitation hardened to give high physical strength and good conductivity.

JALMES M. KELLY. 

